>Hi,
>
>I am creating my first trigger that will set the value of all foreign keys to empty string ('') when user deleted a row in the parent table.
>
>Here is the draft of my code:
>
>

>ALTER TRIGGER [my_parent_delete] 
>   ON  [dbo].[my_parent_table] 
>   INSTEAD OF DELETE
>AS 
>BEGIN
>    SET NOCOUNT ON;
>
>    DECLARE @C_KEY_VALUE CHAR(10)
>
>    -- Get the value of the key/unique field that user wants to delete.
>    SELECT @C_KEY_VALUE FROM DELETED
>
>    -- Update Child 1
>    UPDATE my_child1_table SET foreign_key_fld = '' WHERE foreign_key_fld = @C_KEY_VALUE
>    -- Update Child 2
>    UPDATE my_child2_table SET foreign_key_fld = '' WHERE foreign_key_fld = @C_KEY_VALUE
>    -- Update Child 3,4, etc.
>
>    -- Now delete this row from the parent table
>   delete from my_parent_table WHERE EXISTS 
>	( SELECT * FROM DELETED WHERE my_parent_table.my_unique_fld = DELETED.my_unique_fld )
>
>END
>

>
>My question is, what if any of the child updates fails, how do I "trap" this error? TIA.

If one of the child update fails, most likely the whole trigger will rollback.
Also, your trigger is written the way that it can only handle 1 record deletion in a parent table. You should at least add some preventive code, e.g.

if (select count(*) from Deleted) >1
  begin
   raiserror ('This trigger can only work with single record deletion!',16,1)
   rollback
   return
  end